Field of the Invention
The present invention relates most generally to lighting apparatus, and more particularly to recessed lighting, and still more particularly to an IC-rated and airtight recessed light housings.
Background Discussion
Recessed lighting may be installed at the time of construction prior to ceiling installation or as part of a remodel job after ceiling installation. In either case, a portion of the recessed lighting fixture generally occupies a space partly through the ceiling material, but the principal portion occupies a space above the plane of the ceiling substrate backside. Remodel recessed lighting involves creating a hole for the light housing, connecting the lamp portion of the light to a power source, and securing the housing within the hole, typically with bar hangers that fasten to framing members or with spring-based clamps that sandwich the ceiling substrate between a flange or ring circumscribing the housing.
As is well known, lamps, whether illuminated using low energy LED or conventional incandescent lamp sources, create and radiate considerable heat. Thus, housings have been devised to absorb and dissipate heat and, if not airtight, to allow heated air to escape the housing at a safe rate and in predetermined amounts, not to exceed specified upper limits. Such limits are defined and imposed by codes and regulations promulgated for safety and are published for industry review and compliance by standards organizations, such as the International Electrotechnical Commission and ASTM International, and safety and certification companies for electrical devices and components, such as UL LLC, the OSHA NRTL laboratories.
The most pertinent standards for the present invention can be found embodied in ASTM e283, which governs rate of air leakage through windows, curtain walls, and doors; IEC 60598-1:2014, which specifies general requirements for luminaires, incorporating electric light sources for operation from supply voltages up to 1,000 V, and sets standards for luminaires suitable for direct mounting in or on normally flammable surfaces when thermally insulating material may cover the luminaire; and UL 1598, which sets safety standards for luminaires. The IEC 60598 separates luminaires into two classes: (1) those for recessing into ceilings having thermal insulating material covering the luminaire (IC-rated); and (2) those for recessing into ceilings but not suitable for covering with thermal insulating material (non-IC-rated).
Under the applicable standards identified above, a light fixture may be rated for direct contact with insulation, and thus may bear an “IC” rating, only if it is approved for zero clearance insulation cover by an OSHA NRTL laboratory,” such as UL. Because many homes have blown cellulose insulation covering light fixtures, an IC rating is essential for the safe use of recessed lighting. Where a non-IC light fixture is installed in a space (typically an attic or other space above a ceiling) that contains insulation, at least 3 inches of clearance must be provided on all sides of the luminaire.
A certified air tight luminaire is generally defined under the standards as one showing air leakage less than 2.0 CFM at 75 Pascals when tested in accordance with the ASTM E283 testing method. More colloquially, airtight means that the luminaire housing will not allow air to escape into the ceiling or attic space above the ceiling. This reduces heat loss and cool air loss.
Because conduction is a more efficient method of heat transfer than convection, it would be advantageous to include a lamp assembly that comprises the structures most directly and significantly heated in a recessed lighting luminaire, it would be advantageous to facilitate heat flow from the heat source as directly to the heat sink as possible. A solid-to-solid contact from lamp assembly components to a conductor also in solid-to-solid contact with the heat sink would be advantageous.
At present, there are no known IC-rated, certified airtight luminaires having a lamp assembly in direct physical contact with the housing, wherein the housing and heat sink assembly are also integrally formed, such that the housing functions as both the mounting structure for the lamp assembly and the heat sink so as to maximize heat flow through and away from the luminaire.
Further, known prior art luminaires having means for adjusting the angle of the illumination source either affix the lamp holder assembly to the trim components of the luminaire, or entail changing the angle of the luminaire housing, thereby requiring that the housing tip relative to the plane of the upper surface of the ceiling, and thereby render it at least impracticable to use in an insulated space or in ceiling substrates of any substantial thickness, or configure the assembly with at least a portion of the light engine disposed below the ceiling plane.
Still further, known IC-rated airtight luminaires require a double shroud to achieve the ratings and/or to provide gimbal ring type light adjustment, which is the only kind provided that has the feature wherein the light engine is entirely recessed from the plane of the ceiling. Moreover, the outer shroud is often larger than the ceiling opening, requiring that the luminaire be installed prior to ceiling installation.